1. Field of the Invention
The present invention relates to a photovoltaic module, a photovoltaic module array, a photovoltaic system (photovoltaic power generation apparatus), and a method of detecting failure of a photovoltaic module.
2. Related Background Art
With the recent spreading use of photovoltaic modules, there is a rapidly growing demand for photovoltaic modules suitable for use in medium-scale electric power systems installed outdoors, particularly in the personal houses. Generally, in the case of using the photovoltaic module for electric power generation, a plurality of the photovoltaic modules are connected in series (hereinafter, referred to as xe2x80x9cstringxe2x80x9d) for generating a voltage not smaller than a certain value, and a plurality of the strings are connected in parallel to form a photovoltaic module array.
FIG. 29 is a circuit diagram showing the constitution of a conventional photovoltaic module. In FIG. 29, there are shown a photovoltaic module 1, a photovoltaics 1a, and a bypass diode 1b connected parallel to the photovoltaics 1a. When a shadow is partly formed on the photovoltaic module 1 thereby increasing the electrical resistance of the photovoltaics 1a and causing the application of voltage generated in other modules within the string as an inverse bias to the module 1 (hereinafter, referred to as xe2x80x9cpartial shadowxe2x80x9d), the bypass diode 1b prevents the application of an inverse bias to the photovoltaics 1a in the photovoltaic module 1 thereby preventing the damage of the photovoltaic cell. Also, when a photovoltaic module which was part of the photovoltaic module array exhibited abnormal output, it was usually necessary, for detecting the position of the failure, to check whether the electrical output is normal in each string, then to interrupt the operation of the photovoltaics-photovoltaic system and to measure the electrical output of each photovoltaic module constituting the string by utilizing the output terminals of each photovoltaic module.
However, since the output terminals are usually provided on the back surface (a surface opposite to a light incident surface) of the photovoltaic module, it was very difficult to locate a failure position by using the output terminals after the installation of the photovoltaic module. On the other hand, if terminals for inspection are provided in each of the modules in such a way that they are exposed to the exterior, they may cause leakage of electricity or danger of electrical shock, thereby causing reliability problems. For these reasons, terminals for inspection were not provided. Consequently, for locating the failed photovoltaic module in a photovoltaic module array, the current flowed in the wiring of the photovoltaic module array is typically measured utilizing a clamping ampere meter.
It is preferable in practical use to have a photovoltaic module provided with current detecting means not exposed to the exterior in order to locate a failed position. An example of such a photovoltaic module includes the photovoltaic module shown in FIGS. 30A and 30B, as disclosed in the Japanese Patent Application Laid-Open No. 6-125105 and the photovoltaic module shown in FIG. 31, as disclosed in the Japanese Patent Application Laid-Open No. 9-148613. In FIGS. 30A and 30B, reference characters 1c and 1d indicate magnetic field generating means, and in FIG. 31 reference character 1e indicates light emitting means. In the photovoltaic module shown in FIG. 30A, a current flows in a bypass diode 1b to generate a magnetic field by the magnetic field generating means 1c. The photovoltaic module shown in FIG. 30B is so constructed that by the electromotive force generated by the photovoltaics 1a, an operation current flows into the magnetic field generating means 1d to generate a magnetic field. The photovoltaic module shown in FIG. 31 is so constructed that a current flows into the bypass diode 1b to turn on the light emitting means 1e. The current detecting means shown in FIG. 30B utilizes an operation current c1 generated during the operation of the photovoltaics 1a, while the current detecting means shown in FIGS. 30A and 31 utilize a current c2 flowing into the bypass diode 1b when the voltage of the photovoltaics 1a is lowered.
However, the conventional method of detecting failure of a photovoltaic module array has the following problems. First, when the photovoltaics fails, a current flowing into the bypass diode is generated only when the failure of the photovoltaics is an open circuit failure, and this method cannot be applied to short circuit failure. Second, the failure may not be detected in some cases, depending on the configuration of the photovoltaic module array. This problem becomes more conspicuous when the photovoltaic module array is equipped with a blocking diode for blocking a reverse current.
An open circuit failure means a failure such as an open circuit of the photovoltaic cell itself constituting the photovoltaics, or, in the case of plural photovoltaic cells constituting the photovoltaics, a failure such as breaking of a wiring connecting such photovoltaic cells.
Also, a short circuit failure means a failure such as a short circuit of the photovoltaic cell itself constituting the photovoltaics (including partial short circuit of the photovoltaic cell itself, the same is applied hereinafter), or, in the case of plural photovoltaic cells constituting the photovoltaics, a failure such as the short circuit of the wiring connecting such photovoltaic cells.
Both the open circuit failure and the short circuit failure are modes of failure, and these failure states (modes) are referred to as the open circuit failure mode and the short circuit failure mode, respectively.
The above two problems will be further explained with reference to FIGS. 32A to 34B. FIGS. 32A and 32B show the cases of a short circuit failure of the photovoltaics 1a in the photovoltaic module. In such situation, regardless of the failure state, a current 2 flows into the failure signal generating means D1 for detecting the failure by the xe2x80x9cabsencexe2x80x9d of the operation current of the photovoltaics 1a. On the other hand, even in the case of a failure state, the current 2 does not flow into the failure signal generating means D2 for detecting the failure by the xe2x80x9cpresencexe2x80x9d of the current flowing into the bypass diode 1b. Distinguishing the failure state from the normal state is not possible in either case, and the failed photovoltaic module in the string cannot be detected. FIGS. 33A and 33B show examples of the photovoltaic module array constituted by connecting plural strings in parallel. FIG. 33A shows the state in the normal operation, while FIG. 33B shows the state in the failure state. Reference character 3 indicates a photovoltaic module array, and 3c indicates blocking diodes for preventing loss resulting from the reverse current generated in the case of generating a voltage difference. In such a configuration, when a photovoltaic module 1A constituting a part of a string 3a fails and reaches an open state, the operation current 2 does not flow through the string 3a at all, as shown in FIG. 33B, if the sum of open circuit voltages Voc2+Voc3 generated in other photovoltaic modules 1B and 1C is lower than the sum of operation voltages V4+V5+V6 of the string 3b. In other words, there is obtained a state that a current does not flow into all the bypass diodes and the photovoltaics constituting the string 3a. Consequently, it is not possible to detect the failed photovoltaic module in the string 3a. 
FIGS. 34A and 34B are circuit diagrams showing an example of the photovoltaics module array formed by connecting in series a plurality of parallel members 3e of the photovoltaics. FIG. 34A shows the state in the normal operation, while FIG. 34B is an equivalent circuit diagram showing a failure state. In FIG. 34A, I1+I2 indicates the operation current 2 in a normal operation. Even when a photovoltaic module 1D is damaged to generate an open circuit failure as shown in FIG. 34B, if the load current I1xe2x80x2+I2xe2x80x2 is not larger than the operation current of the non-failed photovoltaic module 1E, reverse bias is not applied to the failed photovoltaic module 1D at all, so that no current flows into the bypass diode in such module. Consequently, the failure cannot be detected by the type means of detecting the failure by the current flowing into the bypass diode.
It is possible to locate a failure point by detecting the operation current of the photovoltaics by employing the constitution as shown in FIG. 30B. However, since the signal generating means 1d such as the magnetic generating means is connected in series to the photovoltaics, the almost amount of the operation current of the photovoltaics flowed into the signal generating means almost the all amount of the operation current of the signal generating means was not small, and this loss becomes a large value which is not negligible particularly in a large-area photovoltaic module of a large current.
The present invention has been accomplished in consideration of the above-described problems in the prior art. An object of the present invention is to provide a photovoltaic module, a photovoltaic module array, a photovoltaic system and a method of detecting a failed photovoltaic module, wherein a failure is detected by locating the failed photovoltaic module, regardless of the constitution of the photovoltaic module array and the failure mode of the photovoltaic module.
Namely, a photovoltaic module of the present invention comprises a photovoltaics and a signal generating means for generating a signal by application of a voltage, wherein the photovoltaics and the signal generating means are connected in parallel and the voltage is a voltage outputted by at least the photovoltaics which is connected in parallel with the signal generating means.
The photovoltaic module of the present invention also comprises a photovoltaics and a discrimination means for generating a signal by application of a predetermined voltage, wherein the discrimination means includes a signal generating means for generating a signal in response to a signal generated by the discrimination means, the photovoltaics and the discrimination means are connected in parallel, and the voltage is a voltage outputted by at least the photovoltaics which is connected in parallel with the discrimination means.
The photovoltaic module of the present invention further comprises a photovoltaics and a signal generating means for generating a signal by application of an electrical power, wherein the photovoltaics and the signal generating means are connected in parallel and in series.
The photovoltaic module of the present invention further comprises a photovoltaics and a discrimination means for generating a signal by application of a predetermined electric power, wherein the discrimination means includes a signal generating means for generating a signal in response to a signal generated by the discrimination means, and the photovoltaics and the discrimination means are connected in parallel and in series.
The photovoltaic module comprises a single photovoltaic cell, a string composed of a plurality of photovoltaic cells connected in series, or a parallel member composed of a plurality of the photovoltaic cells connected in parallel (the same meaning of the photovoltaic module is applied hereinafter).
The signal generating means is preferably a light emitting means, a magnetic field generating means, an electric field generating means, a mechanical displacement generating means, a color development means or a combination thereof.
The signal generating means preferably includes a switching means.
The photovoltaic module preferably further comprises a bypass diode; the photovoltaics, the signal generating means and the bypass diode are preferably connected in parallel.
The photovoltaic module is preferably integrated with a construction material.
The photovoltaic module integrated with the construction material preferably further is integrated with a roof panel member.
The signal generating means is preferably provided in the roof panel member.
The photovoltaic module array of the present invention comprises the above photovoltaic module.
In the photovoltaic module array, a wiring for mutually electrically connecting the above photovoltaic modules is preferably provided at a position other than a surface of the photovoltaic module.
The photovoltaic module array preferably comprises a blocking diode.
Further, the photovoltaic system of the present invention comprises the above photovoltaic module array.
Additionally, the method of the present invention of detecting a failed photovoltaic module comprises obtaining information based on at least an operation voltage or power of each photovoltaic module and searching for the presence or absence of failure in each photovoltaic module constituting a photovoltaic module array.
According to the present invention, the signal generating means or the discrimination means can generate a signal by application of a voltage or a power outputted by at least the photovoltaics which is connected in parallel with one of the signal generating means and the discrimination means. Therefore, it is possible to detect a failure, regardless of the failure mode of the photovoltaic module and the constitution of the photovoltaic module array, and to locate the failed cell module. Namely, since a closed circuit is formed by the signal generating means, the discrimination means and the photovoltaics connected in parallel to these means, for example, in the case of generating a failure in a part of the string of the photovoltaic module, the photovoltaics in the closed circuit other than the failed part operate. Therefore, even when the failure is an open circuit failure or a short circuit failure, it is possible to discover failure generation and locate the failed photovoltaic module.
The open circuit failure and the short circuit failure can be also discriminated by the constitution of the signal generating means.
Further, since the signal generating means or the discrimination means is connected in parallel to the photovoltaics (when the photovoltaic module has a bypass diode, since the photovoltaics, the bypass diode and the signal generating means or the discrimination means are connected in parallel), the full amount of operation current does not necessarily flow into the signal generating means or the discrimination means. Therefore, it is possible to remarkably prevent power loss in the signal generating means or the discrimination means.
Furthermore, in the case where no discrimination means is used, the signal generating means analogically generates signals (strong or weak signal). In the case where discrimination means is used in addition to the signal generating means, the discrimination means generates signals by application of a predetermined voltage or power, and the signal generating means generates a signal; and then in response to this signal, the signal generating means generates another signal, namely the signal generating means digitally generates a signal (ON or OFF signal), whereby it is possible to more easily discriminate whether or not the output of a photovoltaic module is good.
Additionally, in order to detect the failed photovoltaic module, the present invention does not utilize the terminals used in the prior art for detecting an output provided at each photovoltaic module, and therefore the reliability of the photovoltaic module of the present invention has been improved in this way.